A105351 Number of divisors of 135...(2n-1), the concatenation of the first n odd numbers.

1, 2, 8, 4, 4, 16, 4, 32, 20, 2, 16, 12, 12, 4, 24, 2, 32, 64, 128, 16, 96, 32, 16, 64, 32, 4, 32, 32, 16, 96, 32, 8, 256, 2, 16, 60, 8, 32, 12, 64, 48, 480, 32, 128, 512, 16, 128, 192, 2, 128, 96, 32, 64, 160, 64, 16, 6, 64, 64

Offset

1,2

Links

Sean A. Irvine, Table of n, a(n) for n = 1..84

Example

The number of divisors of 13 is 2, hence a(2) = 2.
The number of divisors of 135 is 8, hence a(3) = 8.
The number of divisors of 1357 is 4, hence a(4) = 4.

Maple

R:= 1: x:= 1:
for n from 2 to 49 do
  x:= x*10^(1+ilog10(2*n-1)) + 2*n - 1;
R:= R, numtheory:-tau(x);
od:
R; # Robert Israel, Mar 02 2023

Mathematica

ParallelTable[Divisors[FromDigits[Join@@IntegerDigits/@Table[1+2*k, {k, 0, n}]]]//Length, {n, 0, 48}] (* J.W.L. (Jan) Eerland, Mar 02 2023 *)

Crossrefs

Sequence in context: A194940 A195920 A227334 * A178592 A348683 A301389

Adjacent sequences: A105348 A105349 A105350 * A105352 A105353 A105354

Keyword

base,nonn,more

Author

Parthasarathy Nambi, Apr 30 2005, Jul 01 2005

Extensions

Edited by N. J. A. Sloane, Aug 23 2008 at the suggestion of R. J. Mathar

a(18)-a(50) from J.W.L. (Jan) Eerland, Mar 02 2023

a(51)-a(58) from Jon E. Schoenfield, Mar 03 2023

Offset corrected by Sean A. Irvine, Mar 24 2023

Status

approved